The Russian airline Metrojet, whose civilian plane crashed in Egypt's Sinai region on Saturday has said that the plane had no technical faults and 'external factors' were responsible for the accident. 

Metrojet, previously known as Kogalymavia, said its Airbus A321 plane flying from Egypt's Sharm el-Sheikh resort to St. Petersburg in Russia was in 'excellent' condition on the day of the crash. 

The Islamic State had claimed that it had downed the civilian plane in retaliation to Russia's airstrikes on Isis targets in Syria.

The Sinai Peninsula, where the plane crashed, is known to have an increasing presence of Isis-affiliated militants who have carried out numerous attacks on security forces in recent months.

However, Egypt and Russia have rubbished the claim with officials citing it was impossible for Isis to have shot down a plane flying at 31,000 feet. 

Reports now suggest the possibility of a bomb placed on board the ill-fated flight that led to the crash that killed all 224 people on board. 

Russian aviation officials had said on Sunday that the plane broke up mid-air while it was flying over the Sinai Peninsula in Egypt. 

Experts have suggested that the plane may have broken into two pieces due to a 'catastrophic failure' and even possibly an explosion on board. 

"Early reports said that [the aircraft] split into two and that suggests a catastrophic failure, not a mechanical failure, but that suggests perhaps an explosion on board. So I'd be much more inclined to think if we have to guess at this stage, it's much more likely to have been a bomb on board rather than a missile fired from the ground," Professor Michael Clarke, director general of the Royal United Services Institute think-tank, told BBC. 

While these are only speculations, officials have said they are not ruling out any possible cause behind the crash until the black boxes reveal more details. 

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